The present invention relates to an antenna attached to a portable transceiver such as a portable telephone and a PHS (personal handy phone) terminal and, more particularly, to an antenna with an illuminant attached to the top of a rod-shaped antenna element and lit by high-frequency energy generated on the rod-shaped antenna element during the operation of the transceiver.
One example of a conventional antenna is disclosed in Jpn. U.M. Appln. KOKAI Publication No. 5-9008. This antenna has an illuminant such as a semiconductor light emitting device. The illuminant is mounted on the top of a very-high-frequency whip antenna element or an ultra-high-frequency whip antenna element such that the distribution of high-frequency voltages of the antenna element has the maximum, and turned on by the output power of a transmitter.
When the transmitter is operated to emit a radio wave from the antenna element, a high-frequency voltage is applied to one of terminals of the illuminant, while the other terminal thereof is connected to the earth through stray capacity in the air. Thus, current flows through the illuminant, and the illuminant is lit by the output power of the transmitter.
The above-described antenna can be employed as an antenna assuming a very interesting characteristic that the illuminant mounted on the top of the antenna element is lit without providing a specific lighting power supply or lighting circuit.
Since the illuminant of the above conventional antenna is automatically turned on during the operation of the transmitter, a display function of indicating the operation state and the present location of the antenna can be fulfilled. Since, moreover, the antenna does not need any specific power supply device or the like, its structure is simple and its manufacture is easy.
The conventional antenna described above, however, has the following drawback. The antenna is not so high in operating efficiency that it cannot be turned on quickly if the output power of the transmitter is lowered.
Generally, a portable telephone is employed lowering its output in an area of a strong electric field in order to lessen the consumption of an incorporated battery as much as possible and lengthen the use time of the portable telephone.
If the conventional antenna mounted with an illuminant is applied to the above portable telephone, the output of the portable telephone is lowered when the telephone is used in an area of a strong electric field. Thus, high-frequency energy generated on a rod-shaped antenna element becomes small and the illuminant is not turned on.